This invention relates to methods and apparatus for the alignment and assembly of opto-electronic components in general and, more particularly, to precision alignment and assembly of microelectromechanical (xe2x80x9cMEMxe2x80x9d) components for use in fiber-optic networks.
In order to facilitate the large volume production of fiber-optic telecommunication assemblies, it is necessary to develop high productivity methods for manufacturing precision opto-mechanical assemblies. This includes avoiding, as much as possible, (1) the need to actively align components using measured optical performance as feedback, and (2) the need to maintain high mechanical tolerances during assembly so as to achieve the required optical performance.
The assembly of fiber-optic telecommunication components often include the alignment of an optical element (e.g., an optical filter, an optical switch pump laser, a Fabry-Perot tunable filter, a vertical cavity surface emitting laser, etc.) to a lens (or a system of lenses) which directs light to or from the optical element. Significantly, many new MEM-based devices of the sort which may be used in fiber-optic component assemblies have a well-defined geometric pattern in a plane perpendicular to the optical axis of the device. See, for example, pending prior U.S. patent application Ser. No. 09/105,399, filed Jun. 26, 1998 by Parviz Tayebati et al. for MICROELECTROMECHANICALLY TUNABLE, CONFOCAL, VERTICAL CAVITY SURFACE EMITTING LASER AND FABRY-PEROT FILTER, which patent application discloses tunable Fabry-Perot filters and tunable vertical cavity surface emitting lasers (VCSEL""s). The fact that many new optical devices have the aforementioned well-defined geometric patterns opens up new possibilities for utilizing machine vision systems to assist in the precision alignment and assembly of fiber-optic components.
Some known methods for assembling lens systems utilize the imaging of light propagating through a machine vision system to measure the centers of lenses in the assembly. However, these methods do not involve imaging or utilizing the images of any geometrical features of the components that are being assembled.
Other assembly methods are known in which the alignment of components is based solely on images of the geometrical features of those components. In these latter types of alignment techniques, the component is imaged before it is positioned in its assembly rather than during the positioning operation. However, such alignment methods are highly susceptible to positioning errors due to any movement that occurs after imaging, and also due to movement that occurs while positioning the component. Very precise positioning mechanisms can be utilized to reduce the errors induced by these movements. However, these high precision positioning mechanisms add significantly to the cost of manufacturing the overall product.
As a result, one object of the present invention is to provide novel apparatus for the precise alignment and assembly of opto-electronic components.
Another object of the present invention is to provide a novel method for the precise alignment and assembly of opto-electronic components.
With the above and other objects in view, as will hereinafter appear, there is provided a method for aligning a lens and an opto-electronic device for assembly into a discrete package, the method comprising:
producing a light beam of a selected shape and wavelength and directing it along a selected path to an imaging device, whereby a first spot image of the light beam is formed on the imaging device;
recording the first spot image produced on the imaging device;
determining the coordinates of the center of the first spot image;
positioning a lens so that (a) it intersects the axis of the light beam and (b) its center axis extends substantially parallel to the axis of the light beam, whereby the light beam passes through and is modified by the lens and a second spot image of the modified light beam is formed on the imaging device;
recording the second spot image produced on the imaging device;
determining the coordinates of the center of the second spot image;
moving, while the light source is energized, the lens laterally of the light beam until the center of the second spot image coincides with the center of the first spot image;
positioning a selected opto-electronic device with an optical axis between the lens and the imaging device so that (a) it is adjacent to the lens, (b) it intersects the center axis of the light beam and (c) its optical axis extends substantially parallel to the axis of the light beam;
producing, while the light source is de-energized, an image of the opto-electronic device on the imaging device;
recording the image of the opto-electronic device;
comparing the image of the opto-electronic device with a pre-recorded geometrical pattern and determining from such comparison the X and Y coordinates of the optical axis of the opto-electronic device; and
moving the opto-electronic device until the X and Y coordinates of its the optical axis coincide with the recorded coordinates of the second spot image.
In another aspect of the invention, there is provided an apparatus for aligning a lens and an opto-electronic device for assembly into a discrete package, the apparatus comprising:
a fixed light source for producing light of a selected wavelength, and optical means for transmitting that light as an initial beam;
a first manipulator for supporting a lens in the path of the initial beam and for moving that lens on command along mutually orthogonal X and Y axes that extend perpendicular to the initial beam, the lens being adapted to transmit and shape the initial beam so as to produce a modified beam;
a second manipulator for supporting an opto-electronic device in the path of the initial beam and for moving the opto-electronic device on command along mutually orthogonal X and Y axes that extend perpendicular to the initial beam;
a machine vision system comprising (a) an imaging device positioned to record an image of the initial beam, a lens-modified image of the initial beam produced by a lens carried by the first manipulator and a visible light image of an opto-electronic device carried by the second manipulator, and (b) a programmed means for generating a first error signal representative of the position of the center of the image of the lens-modified beam relative to the center of the image of the initial beam, and a second error signal representative of the position of the optical center of the opto-electronic device relative to the position of the center of the image of the lens-modified beam; and
means for applying the first and second error signals to the first and second manipulators, respectively, so as to (a) cause the first manipulator to move in the X and/or Y directions to the extent required to make the center of the lens-modified beam coincide with the center of the initial beam and (b) cause the second manipulator to move in the X and/or Y directions to the extent required to make the optical center of the opto-electronic device coincide with the center of the lens-modified beam.
And in another aspect of the invention, there is provided a method for aligning a lens and an opto-electronic device for assembly into a discrete package, the method comprising:
(a) providing: (1) a light source for producing a beam of light that emulates the light which will exist in the package during its intended operation, and optical means for shaping that beam, (2) first and second manipulators each adapted to support a component and to move the supported component along mutually orthogonal X and Y axes that are perpendicular to the optical axis of the beam of light, and (3) a machine vision system having an imaging device that is aligned with the light source, the machine vision system being electrically coupled to the first and second manipulators so as to electrically control operation of the manipulators;
(b) energizing the light source so as to produce an initial image of the cross-sectional shape of the beam on the imaging device;
(c) operating the machine vision system so as to determine and record the center of the initial image;
(d) supporting a lens on the first manipulator so that the center axis of the lens extends substantially parallel to the beam;
(e) while the light source is energized, operating the first manipulator so that the center axis of the lens substantially coincides with the longitudinal axis of the beam, whereby the lens shapes the beam to produce a modified beam;
(f) operating the machine vision system so as to record the image of the cross-sectional shape of the modified beam formed on the imaging device;
(g) operating the machine vision system so as to determine the center of the recorded image of the modified beam;
(h) operating the machine vision system so as to compare the center of the modified image with the center of the initial image and to produce a correction signal representing the differences between the centers along the X and Y axes;
(i) using the correction signal to operate the first manipulator so as to move the lens along the X and/or Y axes until the center of the modified image coincides with the center of the initial image;
(j) supporting an opto-electronic device on the second manipulator so that the center axis of the opto-electronic device extends substantially parallel to the beam;
(k) operating the second manipulator so that the center of the opto-electronic device substantially coincides with the longitudinal axis of the beam;
(l) while the light source is de-energized, operating the machine vision system to record a visible light image of the opto-electronic device;
(m) operating the machine vision system to analyze the visible light image and determine therefrom the location of the optical axis of the opto-electronic device;
(n) operating the machine vision system so as to compare the center of the visible image with the center of the modified image and to produce a second correction signal representing the differences between the centers along the X and Y axes; and
(o) using the second correction signal to operate the second manipulator so as to move the opto-electronic device along the X and/or Y axes until the center of the visible image coincides with the center of the modified image.
In still another aspect of the invention, there is provided an apparatus for aligning a lens and an opto-electronic device for assembly into a discrete package, the apparatus comprising:
a fixed light source for producing light of a selected wavelength, and optical means for transmitting that light as an initial beam along a selected path;
a first manipulator for supporting a beam-modifying lens along the path and for moving the lens on command along mutually orthogonal X and Y axes that extend perpendicular to the path;
a second manipulator for supporting an opto-electronic device along the path and for moving the opto-electronic device on command along mutually orthogonal X and Y axes that extend perpendicular to the path;
a machine vision system comprising (a) an imaging device positioned to record an image of the initial beam, images of the beam as modified by a lens carried by the first manipulator and visible light images of an opto-electronic device carried by the second manipulator, and (b) programmed means for generating a first error signal representative of the position of the center of the image of the initial beam in relation to the position of the center of the image of the beam as modified by a lens carried by the first manipulator and a second error signal representative of the position of the optical center of the opto-electronic device relative to the position of the center of the image of the beam as modified by a lens carried by the first manipulator; and
means for applying the first and second error signals to the first and second manipulators respectively so as to (a) cause the first manipulator to move in the X and/or Y directions to the extent required to make the center of the image of the beam as modified by a lens carried by the first manipulator coincide with the center of the initial beam and (b) cause the second manipulator to move in the X and/or Y directions to the extent required to make the optical center of the opto-electronic device coincide with the center of the image of the beam as modified by a lens carried by the first manipulator.
And in still another aspect of the present invention, there is provided an apparatus for optically aligning an opto-mechanical device and a lens for directing light of a selected wavelength to and from the opto-mechanical device, the apparatus comprising:
a machine vision system comprising a camera having an electronic imaging device;
means for producing a light beam and directing it along a selected path to the camera, whereby to produce a spot image of the light beam on the imaging device;
a first X-Y axis manipulator for supporting a lens to be aligned; and
a second X-Y manipulator for supporting an opto-mechanical device to be aligned with the lens;
the vision system also including a memory and a computer programmed to operate the camera and the first and second manipulators so as to execute the following steps: record an initial spot image of the beam and determine the coordinates of the center of the spot image, operate the first manipulator so that a lens supported thereby will intercept and modify the beam and produced a modified spot image on the imaging device, record the modified spot image, determine the coordinates of the center of the modified spot image and operate the first manipulator until the coordinates of the center of the modified spot image coincide with the coordinates of the center of the initial spot image, operate the second manipulator so that an opto-mechanical device supported thereby will be disposed in the path, produce an image of the opto-mechanical device on the imaging device and record that image, analyze the image of the opto-mechanical device to determine its optical center, and operate the second manipulator until the optical center of the opto-mechanical device coincides with the optical center of the modified spot image.